Thomas Test

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Purpose

The Thomas Test measures hip flexor length and distinguishes tightness between one joint and two joint muscles. Hip flexor length directly correlates to the available range of motion at the hip and knee joints.

• Impaired range of motion of the hip may be an underlying cause to other conditions such as: psoas syndrome; patellofemoral pain syndrome; lower back pain, osteoarthritis; rheumatoid arthritis.

Image: Overview of the hip and thigh - anterior and posterior views

Relevant Anatomy

Various muscles are tested during the Thomas test including:

Hip Flexor Muscle	Picture (Muscle in Green)	Number of Joints Crossed	Main Function	Additional Movement
Iliopsoas: Composed of iliacus and psoas major		One joint: Hip	Hip flexion	Hip external rotation
Pectineus		One joint: Hip	Hip flexion	Hip abduction
Adductor Longus & Brevis		One joint: Hip	Hip adduction	Hip flexion and external rotation
Adductor Magnus		One joint: Hip	Adductor part: Hip flexion, adduction, external rotation	Hamstring part: Hip extension and internal rotation
Rectus femoris		Two joints: Hip and knee	Hip flexion	Knee extension
Tensor fascia lata		Two joints: Hip and knee	Hip abduction, flexion, internal rotation	Knee extension
Sartorius		Two joints: Hip and knee	Hip flexion, abduction, external rotation	Knee flexion

"The copyright holder has given special permission to use these images in Physio-pedia"

This 16 minute video is a good summary of the lower extremity muscles.

How to Remember Every Muscle of the Lower Limb and Leg | Corporis

Equipment

The following equipment is needed to perform the Thomas test:

• Stable/firm table.
• Goniometer.
• Chart for recording findings.

Technique

Starting Position: Patient is standing at the end of a table with their gluteal folds on the edge (the same starting position ensures consistency amongst additional tests). The examiner places one hand behind the patient’s knee and another behind their back before helping them to lay back on the table with their knee flexed. The clinician will apply a posterosuperior stabilization force to the ASIS on the side being tested. This stabilization force ensures the pelvis maintains a neutral position. If the pelvis is not stabilized and moves into an anterior tilt, the hip flexors might appear to have an appropriate length, giving a false negative. The patient will keep the unaffected leg flexed, and slowly lower the affected leg, letting it extend as far as possible.

Correct Testing:

• Examiner helps to lay the patient onto the table
• Low back and sacrum are flat on the table
• The non-test leg is in 90 degrees of hip flexion (perpendicular to the table)
  • Helps to improve accuracy across tests/retests

Errors in Testing:

• Patient lays back on their own- unless doing the modified test
• Patient pulls hip into too much flexion, creating a posterior tilt of the pelvis which pulls the thigh off table
• Low back and sacrum are not flat on the table
• Bringing both hips into flexion- allows excessive posterior tilt of the pelvis
• Improper pelvic stabilization- allows pelvic anterior tilt, giving the appearance of normal hip flexor length

Modified Version: The patient is positioned sitting at the end of an examination table. The patient is then asked to lie down while bringing both knees to their chest. They should then perform a posterior pelvic tilt- flat back. One limb should then be lowered towards the table while keeping the opposite tucked towards their chest.

Viewing

The following videos demonstrate how to perform the Thomas test and the modified version of the test:

Interpretation

The table below describes various presentations of a positive Thomas test and the muscles affected:

Interpretation table reference.

*Images: X- stabilization of ASIS, arrows- direction of movement

Presentation	Muscle(s) Affected	Signs
Typical length of hip flexors (negative test)	Psoas major and iliacus, rectus femoris, tensor fasciae latae, sartorius, pectineus, adductor longus/brevis/magnus	Posterior thigh touches the table Knee flexes ~ 80°
Shortness of both one-joint and two-joint hip flexors (positive test)	Psoas major and iliacus, rectus femoris, tensor fasciae latae, sartorius, pectineus, adductor longus/brevis/magnus	Posterior thigh does not touch the table Knee extends
Shortness of two-joint hip flexors. (positive test)	Rectus femoris, tensor fasciae latae, sartorius	Posterior thigh touches the table Knee extends
Shortness of one-joint hip flexors. (positive test)	Iliopsoas, pectineus, adductor longus/brevis/magnus	Posterior thigh does not touch table Knee flexes >80°
Shortness of tensor fasciae latae. (positive test)	Tensor fasciae latae	Abduction of the thigh as hip joint extends, lateral deviation of the patella. Knee extension if abduction/adduction is prevented with hip extension. Internal rotation of the thigh and external rotation of the leg on the femur.
Shortness of sartorius. (positive test)	Sartorius	Abduction, flexion, external rotation of the hip and flexion of the knee. Combination of three or more indicates tightness.

A muscle's strength and available length directly correlate to the range of motion at a joint. Two principles describe the relationship between muscle strength, length, and joint range of motion:

Active insufficiency: Occurs when a two joint muscle produces movement at both joints simultaneously and reaches a shortened length where it can no longer generate force. Active insufficiency refers to a lack of muscle strength.

Passive insufficiency: Occurs when a two-joint muscle is in such a lengthened position that it cannot sufficiently permit motion at both joints. Passive insufficiency refers to a lack of muscle length, i.e. the muscle is tight.

Active and passive insufficiency principles describe potential reasons for decreased range of motion at a joint.

Goniometry

Goniometric measurements can assist the clinician in determining the available range of motion at a joint. These goniometric measurements are unique to the individual; therefore, they should be compared bilaterally.

The following are considered to be typical goniometric measurements for the hip and knee:

*A- axis, SA- stationary arm, MA- movement arm

Action	Typical Degrees of Motion	Technique	Picture
Hip Flexion	125°	Supine with knee flexed A: Greater trochanter SA: Aligned with midline of pelvis MA: Aligned with femur (lateral epicondyle)
Hip Extension	10°	Prone with pelvis stabilized A: Greater trochanter SA: Aligned with midline of pelvis MA: Aligned with femur (lateral epicondyle)
Hip Internal Rotation	32°	Seated on table with knee flexed A: Center of patella SA: Aligned perpendicular to the floor MA: Aligned with leg (crest of tibia)
Hip External Rotation	32°	Seated on table with knee flexed A: Center of patella SA: Aligned perpendicular to the floor MA: Aligned with leg (crest of tibia)
Knee Flexion	140°	Supine A: Lateral epicondyle SA: Greater trochanter MA: Lateral malleolus
Knee Extension	0°	Supine with prop under heel A: Lateral epicondyle SA: Greater trochanter MA: Lateral malleolus

Contraindications

Contraindications describe conditions that if present suggest the Thomas test should not be performed. Screening for contraindications is a clinical reasoning responsibility of the evaluating physical therapist.

Absolute contraindications:

• Posterior hip replacement
• Suspected fracture- lower extremity, hip, sacrum

Relative contraindications:

• Acute lumbar instability
• Suspected muscle injury- hip flexors

Reliability

Studies that test the reliability of the Thomas study are very limited.

1. One study demonstrated that the modified Thomas test has a very good inter-rater reliability. Another demonstrated that the modified Thomas test, has an average of only moderate levels of reliability. Further research is required to determine the reliability of the Thomas test.
2. Peeler & Anderson conducted a study in 2006 examining the reliability of the Thomas test for assessing hip range of motion. Their study calls into question the reliability of the technique using both goniometer and pass/fail scoring methods.
3. Boone et al. revealed higher inter-tester reliability for upper-extremity measurements than for lower-extremity measurements, meaning different examiners are more consistent in measuring upper-extremity than lower-extremity range of motion. However, other studies have demonstrated very high intra-rater reliability, meaning the same examiner can consistently obtain similar ROM values.